Pressure vessel

ABSTRACT

A pressure vessel includes: a liner made of a resin and configured to store a pressurized fluid; and a reinforcing layer made of a fiber-reinforced resin provided around an outer peripheral surface of the liner. The liner includes a body portion having a tubular shape and a pair of side-end portions each having a domical shape. One of the side-end portions extends continuously from one of two ends of the body portion, and the other one of the side-end portions extends continuously from the other one of the two ends of the body portion. The liner includes a restriction portion provided at a center of the liner in an axial direction of the body portion. The restriction portion is configured to restrict displacement of the reinforcing layer in the axial direction.

This application is a division of U.S. patent application Ser. No.16/564,374, filed Sep. 9, 2019, which claims priority from JapanesePatent Application No. 2018-183429 filed on Sep. 28, 2018, thedisclosures of which, including the specification, drawings andabstract, are incorporated herein by reference in their entireties.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2018-183429 filed onSep. 28, 2018 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a pressure vessel that includes aliner made of a resin and configured to store a pressurized fluid, and areinforcing layer made of a fiber-reinforced resin provided around anouter peripheral surface of the liner.

2. Description of Related Art

Conventional pressure vessels include a pressure vessel including aliner made of a resin and configured to store a pressurized fluid, suchas a pressurized gas, and a reinforcing layer with which the liner isreinforced from outside the liner (refer to, for example, JapaneseUnexamined Patent Application Publication No. 2015-017641 (JP2015-017641 A)). The reinforcing layer is formed by winding astrip-shaped fiber-reinforced resin around an outer peripheral surfaceof the liner by filament winding (FW).

SUMMARY

However, when the pressure vessel enters a low-temperature andlow-pressure state, the liner made of a resin having a higher linearexpansion coefficient than that of the reinforcing layer contracts inits radial direction and axial direction, and thus a gap may be formedbetween the liner and the reinforcing layer. As a result, the liner andthe reinforcing layer may be displaced relative to each other in theaxial direction of the liner.

The present disclosure provides a pressure vessel having a configurationthat reduces relative displacement between a liner and a reinforcinglayer in the axial direction of the liner.

An aspect of the present disclosure relates to a pressure vesselincluding a liner and a reinforcing layer. The liner is made of a resin.The liner is configured to store a pressurized fluid. The reinforcinglayer is made of a fiber-reinforced resin. The fiber-reinforced resin isprovided around an outer peripheral surface of the liner. The linerincludes a body portion having a tubular shape and a pair of side-endportions each having a domical shape. One of the side-end portionsextends continuously from one of two ends of the body portion, and theother one of the side-end portions extends continuously from the otherone of the two ends of the body portion. The liner includes arestriction portion provided at a center of the liner in an axialdirection of the body portion. The restriction portion is configured torestrict displacement of the reinforcing layer in the axial direction.

According to the foregoing aspect, even when the liner is peeled offfrom the reinforcing layer due to contraction of the liner in the radialdirection and the axial direction, the restriction portion provided atthe center of the liner enables the reinforcing layer to be kept held bythe liner. As a result, it is possible to reduce relative displacementbetween the reinforcing layer and the liner in the axial direction ofthe liner.

According to the foregoing aspect, the restriction portion is providedat the center of the liner, and thus the position at which thereinforcing layer is held by the liner is at the center of the liner.Therefore, an axial force with which each of the domical side-endportions of the liner is peeled off from the reinforcing layer when theliner contracts in the axial direction can be made lower than that in acase where a restriction portion is provided at a position offset fromthe center of the liner (e.g., at a position close to one end of theliner).

In a case where the caps are provided at the respective end portions ofthe liner, during contraction of the liner in the axial direction, thecaps are kept held by the reinforcing layer and thus a contraction forceof the liner acts on the caps in the directions in which the caps aredetached from the liner. However, according to the foregoing aspect, therestriction portion is provided at the center of the body portion of theliner, and therefore, such a contraction force is reduced, and thus theforce acting on the caps due to contraction of the liner is reduced.Note that, the center of the liner in the axial direction of the bodyportion signifies a portion including the center of a region betweenboth ends of the liner in the axial direction.

As long as the restriction portion is provided at the center of theliner, the restriction portion provided on the outer peripheral surfaceof the body portion may be in the form of a spot or may be composed oftwo or more restriction portions that are separated from each other. Inthe foregoing aspect, the restriction portion may extend along thecircumference of the outer peripheral surface of the body portion. Withthis configuration, the restriction portion provided at the center ofthe liner enables the reinforcing layer to be stably held by the liner.The expression “the restriction portion extends along the circumferenceof the outer peripheral surface of the body portion” in the foregoingaspect signifies that an annular (endless) restriction portion isprovided on the outer peripheral surface of the body portion of theliner.

In the foregoing aspect, the restriction portion may be a recessedportion provided in the outer peripheral surface of the body portion,and a part of the fiber-reinforced resin may be disposed in the recessedportion. With this configuration, the liner and the reinforcing layerare engaged with each other by a part of the fiber-reinforced resin,which is disposed in the recessed portion, and thus it is possible toreduce displacement of the reinforcing layer with respect to the linerin the axial direction of the liner.

In the foregoing aspect, the restriction portion may be a projectionportion provided on the outer peripheral surface of the body portion,and the projection portion may be covered with the fiber-reinforcedresin. With this configuration, the liner and the reinforcing layer areengaged with each other by the fiber-reinforced resin with which theprojection portion is covered, and thus it is possible to reducedisplacement of the reinforcing layer with respect to the liner in theaxial direction.

The projection portion, which is an example of the restriction portion,may be formed as a part of the liner, for example, by scraping away apart of the outer peripheral surface of the liner, as long as theprojection portion is provided at the center of the liner. In theforegoing aspect, the projection portion may be a fixed portion providedaround the outer peripheral surface of the body portion so as to projectfrom the outer peripheral surface of the body portion, and fixed to theouter peripheral surface. With this configuration, it is possible toeasily provide a fixed portion having a desired shape and a desired sizeat the center of the liner without the need to scrape away a part of theliner.

The fixed portion is not particularly limited as long as it acts as therestriction portion that is a projection portion. In the foregoingconfiguration, the fixed portion may be a bundle of fibers impregnatedwith a resin, and the resin of the fixed portion may have higheradhesiveness for the outer peripheral surface of the liner thanadhesiveness of the resin included in the fiber-reinforced resin. Withthis configuration, even when the fiber-reinforced resin is peeled offfrom the outer peripheral surface of the liner during contraction of theliner, it is possible to more reliably prevent the fixed portion frombeing peeled off from the outer peripheral surface of the liner.

According to the foregoing aspect of the present disclosure, it ispossible to reduce relative displacement between the liner and thereinforcing layer in the axial direction of the liner.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the present disclosure will be described belowwith reference to the accompanying drawings, in which like numeralsdenote like elements, and wherein:

FIG. 1 is a schematic sectional view of a pressure vessel according to afirst embodiment of the present disclosure;

FIG. 2 is an enlarged sectional view of a portion A of the pressurevessel illustrated in FIG. 1 ;

FIG. 3 is a schematic perspective view of a liner of the pressure vesselillustrated in FIG. 1 ;

FIG. 4 is a schematic perspective view for describing a method ofmanufacturing the pressure vessel illustrated in FIG. 1 ;

FIG. 5A is a schematic perspective view illustrating a modificationexample of the liner of the pressure vessel illustrated in FIG. 1 ;

FIG. 5B is an enlarged sectional view of a main portion in amodification example of the pressure vessel illustrated in FIG. 2 ;

FIG. 6 is a schematic perspective view of a liner of a pressure vesselaccording to a second embodiment of the present disclosure;

FIG. 7 is an enlarged sectional view of a main portion of the pressurevessel including the liner illustrated in FIG. 6 ;

FIG. 8A is a schematic perspective view illustrating a modificationexample of the liner of the pressure vessel illustrated in FIG. 6 ;

FIG. 8B is an enlarged sectional view of a main portion in amodification example of the pressure vessel illustrated in FIG. 6 ;

FIG. 9 is a schematic perspective view illustrating another modificationexample of the liner of the pressure vessel illustrated in FIG. 6 ; and

FIG. 10 is an enlarged sectional view of a main portion of the pressurevessel including the liner illustrated in FIG. 9 .

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, several example embodiments of the present disclosure willbe described with reference to FIG. 1 to FIG. 10 .

First Embodiment

Configuration of Pressure Vessel 1

FIG. 1 is a schematic sectional view of a pressure vessel 1 according toa first embodiment of the present disclosure. FIG. 2 is an enlargedsectional view of a portion A of the pressure vessel 1 illustrated inFIG. 1 . FIG. 3 is a schematic perspective view of a liner 3 of thepressure vessel 1 illustrated in FIG. 1 . FIG. 4 is a schematicperspective view for describing a method of manufacturing the pressurevessel 1 illustrated in FIG. 1 .

As illustrated in FIG. 1 , the pressure vessel 1 is a fuel tankconfigured to store fuel gas, such as hydrogen gas, to be supplied to afuel cell in an in-vehicle fuel cell system. The pressure vessel 1 maybe used for any purposes other than electricity generation by the fuelcell system. Examples of the substance to be stored in the pressurevessel 1 may include not only hydrogen gas serving as fuel gas, but alsovarious kinds of compressed gas, such as compressed natural gas (CNG),various kinds of liquefied gas, such as liquefied natural gas (LNG) andliquefied petroleum gas (LPG), and various other pressurized substances.

The pressure vessel 1 includes the liner 3, caps 2A, 2B, and areinforcing layer 4. The liner 3 is made of a resin and configured tostore a pressurized fluid. The caps 2A, 2B are made of a metal. The cap2A is attached to one end portion of the liner 3, and the cap 2B isattached to the other end portion of the liner 3. The reinforcing layer4 is made of a fiber-reinforced resin. The reinforcing layer 4 isprovided such that an outer peripheral surface of the liner 3 is coveredwith the fiber-reinforced resin and the outer peripheral surface of eachof the caps 2A, 2B is partially covered with the fiber-reinforced resin.

The liner 3 has a storage space 34 for storing fuel gas. The storagespace 34 is defined by a resin having a gas barrier property against thefuel gas. Examples of the resin material of the liner 3 includethermoplastic resins, such as polyethylene, polypropylene, nylonpolyamide, and an ethylene vinyl alcohol copolymer.

The liner 3 includes a body portion 31 having a tubular shape and a pairof side-end portions 32A, 32B each having a domical shape. The side-endportion 32A extends continuously from one end of the body portion 31,and the side-end portion 32B extends continuously from the other end ofthe body portion 31. The storage space 34 for storing gas is providedinside the liner 3. Specifically, the body portion 31 is a cylindricalportion having a predetermined length and extending along a central axisX of the pressure vessel 1 illustrated in FIG. 1 . The side-end portion32A has such an outer contour that the side-end portion 32Ahemispherically bulges out from the one end of the body portion 31.Similarly, the side-end portion 32B has such an outer contour that theside-end portion 32B hemispherically bulges out from the other end ofthe body portion 31. An opening is provided in a top portion of each ofthe side-end portions 32A, 32B. The cap 2A made of a metal is fitted inthe opening of the side-end portion 32A. Similarly, the cap 2B made of ametal is fitted in the opening of the side-end portion 32B.

The cap 2A is made of a metal, such as aluminum or an aluminum alloy.The cap 2A includes a tubular portion 21A that is a main body, and aflange portion 22A provided on the outer periphery of the tubularportion 21A. The fiber-reinforced resin of the reinforcing layer 4 iswound around the flange portion 22A of the cap 2A and the liner 3, withthe flange portion 22A pressed against the outer surface of the side-endportion 32A. A valve (not illustrated) is attached to the cap 2A. Withthe valve, fuel gas is discharged from the pressure vessel 1 or isallowed to flow into the pressure vessel 1.

Like the cap 2A, the cap 2B is made of a metal, such as aluminum or analuminum alloy, and includes a tubular portion 21B that is a main body,and a flange portion 22B provided on the outer periphery of the tubularportion 21B. The fiber-reinforced resin of the reinforcing layer 4 iswound around the flange portion 22B of the cap 2B and the liner 3, withthe flange portion 22B pressed against the outer surface of the side-endportion 32B. The inside of the tubular portion 21B of the cap 2B issealed, and thus the storage space 34 is hermetically sealed by the cap2B.

The reinforcing layer 4 is made of a fiber-reinforced resin (referredalso to as “fiber-reinforced plastic (FRP)”) including reinforcingfibers (filaments) aligned in one direction and impregnated with amatrix resin. In the present embodiment, the fiber-reinforced resin iswound by hoop winding and helical winding such that multiple layers areformed on the outer peripheral surface of the liner 3 and an exposedportion of the outer peripheral surface of each of the caps 2A, 2B.

Examples of the reinforcing fibers include glass fibers, carbon fibers,aramid fibers, alumina fibers, boron fibers, steel fibers,poly-p-phenylenebenzobisoxazole (PBO) fibers, natural fibers, andhigh-strength polyethylene fibers. In the present embodiment, a carbonfiber-reinforced resin (referred also to as “carbon fiber-reinforcedplastic (CFRP)”) including carbon fibers serving as reinforcing fibersis wound around the outer peripheral surface of the liner 3, and a glassfiber-reinforced resin (referred also as “glass fiber-reinforced plastic(GFRP)”) including glass fibers serving as reinforcing fibers is furtherwound around the outer peripheral surface of the liner 3.

In the present embodiment, a thermosetting resin is used as the matrixresin. Examples of the thermosetting resin include an epoxy resin,modified epoxy resins typified by a vinyl ester resin, a phenol resins,a melamine resins, a urea resin, an unsaturated polyester resin, analkyd resin, a polyurethane resin, and a thermosetting polyimide resin.

In the present embodiment, a thermosetting resin is used as the matrixresin. However, a resin with which a bundle of fibers is impregnated maybe a thermoplastic resin as long as the thermoplastic resin can beheated to a softening point (glass transition point) or higher. Examplesof the thermoplastic resin include a polyester resin, a polypropyleneresin, a nylon resin (e.g., a 6-nylon resin or a 6,6-nylon resin), apolyamide resin, a polycarbonate resin, an acrylic resin, and anAcrylonitrile Butadiene Styrene (ABS) resin.

In the present embodiment, a restriction portion is provided at thecenter of the liner 3 in a direction along the central axis X (the axialdirection) of the body portion 31. The restriction portion has such ashape as to restrict displacement of the reinforcing layer 4 in theaxial direction. As illustrated in FIG. 2 , an example of therestriction portion is a recessed portion 33A provided in the outerperipheral surface of the body portion 31, and a part of thefiber-reinforced resin of the reinforcing layer 4 is disposed in therecessed portion 33A. In the present embodiment, the fiber-reinforcedresin may be disposed in the recessed portion 33A in any manner, as longas the fiber-reinforced resin of the reinforcing layer 4 does not comeout of the recessed portion 33A (that is, as long as thefiber-reinforced resin is kept engaged with recessed portion 33A) evenwhen the liner 3 contracts in the radial direction. The maximum depth ofthe recessed portion 33A is desirably set to such a depth that thefiber-reinforced resin of the reinforcing layer 4 does not come out ofthe recessed portion 33A of the liner 3 when the liner 3 contracts inthe radial direction. It is desirable to set the maximum depth of therecessed portion 33A to a depth greater than the maximum amount by whichthe liner 3 contracts in the radial direction under a given usageenvironment of the pressure vessel 1.

In the present embodiment, the recessed portion 33A is an annular grooveextending along the circumference of the outer peripheral surface of thebody portion 31. The recessed portion 33A is a concave portion recessedwith respect to the outer peripheral surface of the liner 3, in asection taken along the axial direction of the liner 3. Specifically, awall surface that defines the recessed portion 33A (a side wall surfacethat defines the groove) is a curved wall surface. With thisconfiguration, it is possible to reduce the stress to be concentrated onthe recessed portion 33A of the liner 3 when the reinforcing layer 4 isengaged with the recessed portion 33A. The width of the recessed portion33A (groove width) is not limited to any particular width, and may be,for example, within a range of 5% to 15% of the total length of theliner 3.

The recessed portion 33A can be formed, for example, by scraping away aportion of a conventional liner. However, the recessed portion 33A maybe formed in any method. For example, the recessed portion 33A may beformed by deforming a wall portion of the body portion 31 of the liner 3with the thickness of the liner 3 kept substantially constant.

In the present embodiment, the center of the liner 3 where the recessedportion 33A, which is an example of the restriction portion, is providedsignifies a portion including a center line C located at the middle of aregion between both ends of the liner 3. The recessed portion 33A may beany portion including the center line C. Therefore, where the length ofthe liner 3 in its axial direction is denoted by L, the recessed portion33A is provided so as to include a position that is at a distance of L/2from each end of the liner 3 in the axial direction.

In the pressure vessel 1 configured as described above, for example,when the fuel gas is discharged from the pressure vessel 1, the fuel gasadiabatically expands in the storage space 34. This may cause a decreasein the internal pressure of the storage space 34, leading to a decreasein the temperature of the fuel gas in the storage space 34. In thiscase, the liner 3 may contract in its radial direction and axialdirection. Even when the liner 3 is peeled off from the reinforcinglayer 4 due to contraction of the liner 3, the recessed portion 33A (anexample of the restriction portion) provided at the center of the liner3 enables the reinforcing layer 4 to be kept held by the liner 3.Specifically, the liner 3 and the reinforcing layer 4 are engaged witheach other by a part of the fiber-reinforced resin of the reinforcinglayer 4, which is disposed in the recessed portion 33A. As a result, itis possible to reduce displacement of the reinforcing layer 4 withrespect to the liner 3 in the axial direction.

In particular, because the recessed portion 33A, which is an example ofthe restriction portion, is provided at the center of the liner 3, theposition at which the reinforcing layer 4 is held by the liner 3 is atthe center of the liner 3. Therefore, an axial force with which each ofthe side-end portions 32A, 32B of the liner 3 is peeled off from thereinforcing layer 4 when the liner 3 contracts in the axial directioncan be made lower than that in a case where a restriction portion isprovided at a position offset from the center of the liner 3 (e.g., at aposition close to one end of the liner 3).

In the present embodiment, the caps 2A, 2B are brought into contact withthe respective end portions of the liner 3 from outside of the liner 3,as described above. Therefore, when the liner 3 contracts in the axialdirection, the caps 2A, 2B around which the fiber-reinforced resin isprovided are kept held by the reinforcing layer 4. Thus, a contractionforce of the liner 3 acts on the caps 2A, 2B in the directions in whichthe caps 2A, 2B are detached from the liner 3. However, the recessedportion 33A, which is an example of the restriction portion, is providedat the center of the body portion 31 of the liner 3, and therefore, sucha contraction force is reduced, and thus the force acting on the caps2A, 2B due to contraction of the liner 3 is reduced.

In particular, because the recessed portion 33A extends along thecircumference of the outer peripheral surface of the body portion 31,the recessed portion 33A provided at the center of the liner 3 enablesthe reinforcing layer 4 to be stably held by the liner 3. As long as apart of the fiber-reinforced resin of the reinforcing layer 4 can bedisposed in the recessed portion 33A and the reinforcing layer 4 can bestably held by the liner 3, the recessed portion 33A may be composed oftwo or more recessed portions that are separated from each other, thatare extending in the circumferential direction of the liner 3, and thatare disposed at the center of the liner 3, for example, as illustratedin FIG. 5A.

As long as a sufficient strength of the liner 3 is maintained when thereinforcing layer 4 is engaged with the recessed portion 33A, instead ofthe recessed portion 33A illustrated in FIG. 2 , a recessed portion 33Bdefined by a bottom surface 33 a and side wall surfaces 33 b rising fromthe bottom surface 33 a may be provided, as illustrated in FIG. 5B.

Method of Manufacturing Pressure Vessel 1

A method of manufacturing the pressure vessel 1 will be described below.First, the liner 3 as illustrated in FIG. 3 is produced. Specifically, apre-molded tubular member corresponding to the body portion 31 anddomical members corresponding to the side-end portions 32A, 32B arejoined together. Next, the caps 2A, 2B are fixed to the respective endportions of the liner 3 with, for example, an adhesive. Next, therecessed portion 33A illustrated in FIG. 3 is formed at the center ofthe liner 3 by scraping away a portion of the body portion 31.

In the present embodiment, the recessed portion 33A is formed at thecenter of the liner 3 after the caps 2A, 2B are fixed to the respectiveend portions of the liner 3 with, for example, an adhesive.Alternatively, the recessed portion 33A may be formed in advance in atubular member corresponding to the body portion 31.

A roughening treatment, such as a blasting treatment or an etchingtreatment, may be performed on the surface of the recessed portion 33Aof the liner 3. The surface roughness of the recessed portion 33A isgreater than the surface roughness of the other portion of the outerperipheral surface of the liner 3 than the recessed portion 33A. Thus,the reinforcing layer 4 is easily kept held in the recessed portion 33Adue to an anchoring effect.

Next, a fiber-reinforced resin 41 (prepreg) is prepared. Thefiber-reinforced resin 41 includes continuous reinforcing fibers alignedin one direction and impregnated with an uncured thermosetting resin.The fiber-reinforced resin 41 that has been prepared is in the form of astrip or a string. The fiber-reinforced resin 41 is wound, in layers,around the outer peripheral surface of the liner 3 to which the caps 2A,2B have been attached, while a predetermined winding tension is appliedto the fiber-reinforced resin 41. By filament winding (FW), thereinforcing layer 4 is formed in the following manner. First, thefiber-reinforced resin 41 is moved in the axial direction while theliner 3 is rotated, so that the fiber-reinforced resin 41 is woundaround the outer peripheral surface of the liner 3 by hoop winding whileoverlaps of the fiber-reinforced resin 41 are created (see, for example,FIG. 4 ), and then the fiber-reinforced resin 41 is wound around theliner 3 by, for example, helical winding. At this time, thefiber-reinforced resin enters the recessed portion 33A provided in theouter peripheral surface of the liner 3. Then, the reinforcing layer 4that has been formed is heated to cure the thermosetting resin that hasnot been cured. In this way, the pressure vessel 1 is obtained.

Second Embodiment

Hereinafter, a pressure vessel according to a second embodiment of thepresent disclosure and a method of manufacturing the pressure vesselwill be described with reference to FIG. 6 to FIG. 8B. A pressure vessel1 according to the second embodiment is different from the pressurevessel 1 according to the first embodiment, in the shape of arestriction portion provided on the liner 3. Therefore, the sameportions as those in the first embodiment will be denoted by the samereference numerals, and detailed description thereof will be omitted.

As illustrated in FIG. 6 and FIG. 7 , in the present embodiment, arestriction portion is provided at the center of the liner 3 in theaxial direction of the body portion 31. The restriction portion has sucha shape as to restrict displacement of the reinforcing layer 4 in theaxial direction. As illustrated in FIG. 6 , an example of therestriction portion is a projection portion 34A provided on the outerperipheral surface of the body portion 31, and the projection portion34A is covered with the fiber-reinforced resin of the reinforcing layer4. In the present embodiment, the center of the liner 3 where theprojection portion 34A, which is an example of the restriction portion,is provided signifies a portion including a center line located at themiddle of a region between both ends of the liner 3, as in the firstembodiment. The projection portion 34A may be any portion including thecenter line. It is desirable to set the maximum height of the projectionportion 34A to a height greater than the maximum amount by which theliner 3 contracts in the radial direction.

In the present embodiment, the projection portion 34A is an annularridge extending along the circumference of the outer peripheral surfaceof the body portion 31. The width of the projection portion 34A (ridgewidth) is not limited to any particular width, and may be, for example,within a range of 5% to 15% of the total length of the liner 3. Theprojection portion 34A is a convex portion that bulges with respect tothe outer peripheral surface of the liner 3, in a section taken alongthe axial direction of the liner 3. Specifically, a wall surface thatdefines the projection portion 34A is a curved wall surface. With thisconfiguration, it is possible to reduce the stress to be concentrated onthe projection portion 34A of the liner 3 when the reinforcing layer 4is engaged with the projection portion 34A.

According to the present embodiment, even when the liner 3 is peeled offfrom the reinforcing layer 4 due to contraction of the liner 3, theprojection portion 34A provided at the center of the liner 3 enables thereinforcing layer 4 to be kept held by the liner 3, as in the firstembodiment. Specifically, the liner 3 and the reinforcing layer 4 areengaged with each other by the fiber-reinforced resin of the reinforcinglayer 4 with which the recessed portion 33A is covered. As a result, itis possible to reduce displacement of the reinforcing layer 4 withrespect to the liner 3 in the axial direction. Further, it is possibleto reduce an axial force that acts when each of the side-end portions32A, 32B of the liner 3 is peeled off from the reinforcing layer 4during contraction of the liner 3 in the axial direction. Further, it ispossible to reduce forces acting on the caps 2A, 2B due to contractionof the liner 3.

In particular, because the projection portion 34A extends along thecircumference of the outer peripheral surface of the body portion 31,the projection portion 34A provided at the center of the liner 3 enablesthe reinforcing layer 4 to be stably held by the liner 3. As long as theprojection portion 34A is covered with the fiber-reinforced resin of thereinforcing layer 4 and thus the reinforcing layer 4 can be stably heldby the liner 3, the projection portion 34A may be composed of two ormore projection portions that are separated from each other, that areextending in the circumferential direction of the liner 3, and that aredisposed at the center of the liner 3, for example, as illustrated inFIG.

8A.

As long as a sufficient strength of the reinforcing layer 4 ismaintained when the reinforcing layer 4 is engaged with the projectionportion 34A, instead of the projection portion 34A illustrated in FIG. 7, a projection portion 34B having a rectangular section may be provided,as illustrated in FIG. 8B.

During manufacturing of the pressure vessel 1, the projection portion34A may be formed, for example, by scraping away a portion of aconventional liner before the formation of the reinforcing layer 4.Alternatively, for example, two tubular members having shapes obtainedby splitting the shape of the body portion 31 at the center of the bodyportion 31 are prepared. Then, when end surfaces of the two tubularmembers are brought into contact with each other and joined together bythermal fusion bonding, portions of the two tubular members, whichinclude the end surfaces, are deformed into the projection portion 34A.The projection portion 34A may be formed during molding of a tubularmember corresponding to the body portion 31. After the liner 3illustrated in FIG. 6 is prepared, the reinforcing layer 4 is formed bywinding the fiber-reinforced resin 41 around the outer peripheralsurface of the liner 3 including the projection portion 34A, in the samemethod as the method described with reference to FIG. 4 . As a result,the pressure vessel can be obtained. In this way, the surface of theprojection portion 34A is covered with the fiber-reinforced resin of thereinforcing layer 4.

In FIG. 6 to FIG. 8B, the projection portion 34A, 34B is formed so as tobe integral with the liner 3. Alternatively, for example, as illustratedin FIG. 9 , the projection portion provided on the liner 3 may be afixed portion 34C that is provided around the outer peripheral surfaceof the body portion 31 so as to project from the outer peripheralsurface of the body portion 31 and fixed to the outer peripheral surfaceof the body portion 31. The fixed portion 34C may be made of, forexample, a resin such as a thermosetting resin, or metal as long as thefixed portion 34C functions as a restriction portion. In the presentembodiment, the fixed portion 34C is a bundle of fibers impregnated witha resin.

A resin with which a bundle of fibers is impregnated is desirably aresin having higher adhesiveness (higher affinity) for the outerperipheral surface of the liner 3 than the matrix resin included in thefiber-reinforced resin of the reinforcing layer 4. For example, when theliner 3 is made of a nylon resin (nylon 6, nylon 66, or the like) andthe matrix resin is an epoxy resin, an acrylic modified silicone resinor the like may be an example of the resin with which a bundle of fibersof the fixed portion 34C is impregnated. When the liner is made of apolyethylene resin and the matrix resin is an epoxy resin, cyanoacrylateor the like may be an example of the resin with which a bundle of fibersof the fixed portion 34C is impregnated.

The fixed portion 34C can be obtained by winding, multiple times, abundle of fibers impregnated with an uncured resin around the outerperipheral surface of the body portion 31 at the center of the linerhaving a smooth outer peripheral surface, and then thermally curing theresin. Then, in the same method as the method described with referenceto FIG. 4 , the fiber-reinforced resin 41 is wound around the outerperipheral surface of the liner 3 including the fixed portion 34C toform the reinforcing layer 4. As a result, the pressure vessel 1 isobtained. In this way, as illustrated in FIG. 10 , the surface of thefixed portion 34C is covered with the fiber-reinforced resin of thereinforcing layer 4.

The resin included in the fixed portion 34C is a resin having higheradhesiveness for the outer peripheral surface of the liner 3 than theresin included in the fiber-reinforced resin of the reinforcing layer 4.Thus, even when the fiber-reinforced resin is peeled off from the outerperipheral surface of the liner 3 during contraction of the liner 3, itis possible to more reliably prevent the fixed portion 34C from beingpeeled off from the outer peripheral surface of the liner 3.

Before the fiber-reinforced resin is wound around the outer peripheralsurface of the liner 3, a roughening treatment may be performed on thesurface of the projection portion 34A, the outer surface of theprojection portion 34B or the outer surface of the fixed portion 34C. Inthis way, the surface roughness of the projection portion 34A, theprojection portion 34B or the fixed portion 34C that has been subjectedto the roughening treatment is greater than the surface roughness of theremaining portion of the outer peripheral surface of the liner 3. Thus,due to an anchoring effect, the reinforcing layer 4 is easily kept heldby the projection portion 34A, the projection portion 34B or the fixedportion 34C that has been subjected to the roughening treatment.

Some embodiments of the present disclosure have been described in detailabove. However, an applicable embodiment of the present disclosure isnot limited to the foregoing embodiments, and various design changes maybe made to the foregoing embodiments within the scope of the appendedclaims.

For example, the fixed portion according to the second embodiment ismade of a bundle of fibers impregnated with a resin. Alternatively, thefixed portion may be made of a resin having a higher linear expansioncoefficient than that of the resin material of the liner. In this way,the contraction amount of the fixed portion is greater than thecontraction amount of the resin material of the liner, and therefore,the fixed portion is more reliably fixed to the outer peripheral surfaceof the liner.

What is claimed is:
 1. A pressure vessel comprising: a liner made of aresin, the liner being configured to store a pressurized fluid; and areinforcing layer made of a fiber-reinforced resin, the fiber-reinforcedresin being provided around an outer peripheral surface of the liner,wherein the liner includes a body portion having a tubular shape and apair of side-end portion seach having a domical shape, one of theside-end portions extending continuously from one of two ends of thebody portion, and the other one of the side-end portions extendingcontinuously from the other one of the two ends of the body portion, andthe liner includes a restriction portion provided at a center of theliner in an axial direction of the body portion, the restriction portionbeing configured to restrict displacement of the reinforcing layer inthe axial direction; the restriction portion is a projection portionprovided on an outer peripheral surface of the body portion; and theprojection portion is covered with the fiber-reinforced resin; whereinthe projection portion is a fixed portion provided around the outerperipheral surface of the body portion, the fixed portion projectingfrom the outer peripheral surface of the body portion, and the fixedportion being fixed to the outer peripheral surface; and wherein thefixed portion is a bundle of fibers impregnated with a resin; and theresin of the fixed portion has higher adhesiveness for the outerperipheral surface of the liner than adhesiveness of the resin includedin the fiber-reinforced resin.